Control apparatus



2 SHEETS-SHEET l AGENT CONTROL. APPARATUS D. H. SIEBENTHALER INVENTOR DAViD H SIEBENTHALER Dec. 4, 195] Filed Sept. 5, 1946 D. H. SIEBENTHALER Dec. 4, 1951 CONTROL APPARATUS 2 SHEETSSHEET 2 Filed Sept. 5, 1946 m 0mm Mm mmm R k E m N m H V T m m B E S VI H w Vv. B mfi vow mom HQ Em 9N 2N mmm mm mm m AGENT Patented Dec. 4, 1951 UNITED STATES PATENT OFFICE CONTROL APPARATUS David H. Siebenthaler, Meriden, 001111., assignor, by mesne assignments, to Niles-Bement-Pond Company, West Hartford, Conn., a corporation or New Jersey Application September 5, 1946, Serial N 0. 695,009

12 Claims. 1

This invention relates to control apparatus for regulating a variable condition in response to changes in a controlling condition, which may be the same as the regulated condition or otherwise. In particular, the invention relates to carubretors for internal combustion engines.

The carburetor disclosed is intended for use on aircraft, althought it may be used on other types of engines. Also, the condition control system disclosed herein may be used to control other variable conditions.

Carburetors for internal combustion engines, particularly those used on aircraft, commonly include some means for measuring the rate of air flow to the engine, means for measuring the rate of fuel flow to the engine, means for balancing these two measurements against each other, and means responsive to the balance or unbalance of the two measurements for controlling one or the other of the two flows to maintain a constant fuel-air ratio. Since the density of the air varies, it is common to provide some means for correcting the air flow measuring means or the measurement balancing means for variation in air density.

The present invention includes electrical means for measuring the balance between the fuel and the air flows, and electrical means for compensating the action of the balance measuring means in response to variations in air density. The present invention further contemplates the use of an electrical signal produced by these electrical means to control suitable motor means which regulate the fuel flow. It is proposed to use gas-filled electric discharge tubes of the wellknown Thyratron type to respond to the electrical signal and to control the motor. Such tubes are very sensitive to applied signals. For that reason, they are very desirable in control systems Where a quick response to a small variation in a variable condition is needed. However, these tubes are so sensitive that they are apt to respond to stray electric fields in their vicinity, which fields are not related to the controlled or the controlling conditions. This invention includes a new motor control circuit using Thyratron," wherein the sensitivity characteristics of the tubes are retained, without subjecting the system to undesired control impulses caused by stray electrical fields and other outside influences.

It is therefore an object of the present invention to provide an improved carburetor for an internal combustion engine.

Another object of the present invention is to provide an improved control system for regulat- 2 ing a variable condition in response to a controlling condition.

A further object of the invention is to provide an improved electrical motor control system employing sensitive electrical gas-filled discharge tubes.

Other objects and advantages of the present invention will become apparent from a consideration of the appended specification, claims and drawings, in which Figure 1 represents, somewhat diagrammatically, a carburetor for an internal combustion engine embodying the principles of my invention, with the electrical circuits thereof omitted,

Figure 2 illustrates a modified form of motor control apparatus, which may be used in place of that shown in Figure l, and

Figure 3 illustrates an electrical wiring diagram which may be used in the carburetor of Figure l.

Referring to Figure 1, there is shown a portion of a body 10 of a carburetor, through which air flows from an entrance i2, past a Venturi structure M, a throttle l6 and a fuel discharge nozzle Hi to an outlet 20.

An impact tube 22 conveys air at the impact pressure existing inthe entrance E2 to a chamber 24. The chamber 24 is connected by a conduit 26 to a chamber 28 in a control device generally indicated at 30. The throat of venturi I4 is connected through conduits 32 and 34 to a chamber 36 in the control device 30. The chambers 28 and 36 are separated by a flexible diaphragm 38, and are connected by a fixed restriction 40.

A bellows 42 is mounted in the chamber 24 and carries at its free end a condenser plate 44. A stationary condenser plate 46 is mounted at the opposite end of chamber 24. The condenser plates 44 and 46 together form a variable condenser generally indicated at 48.

Fuel flows through the carburetor of Figure 1 from an inlet 50 through a rotary sliding vane pump 52 and a fixed restriction 54, a conduit 56, a pressure regulator 58 and a conduit 60 to the fuel discharge nozzle l8. By-passing the restriction 54 is a passage including a variable restriction 62 controlled by a valve 64 biased to closed position by a spring 66, and a restriction 68 in series with the restriction 62.

The pressure regulator 58 maintains a constant pressure on the downstream side of restriction 54. The fuel flow is regulated by means of a pressure relief valve 10, which controls a conduit leading from the pump outlet to the pump inlet, and thereby regulates the pressure on the upstream side of restriction 54. Valve I8 is attached to a balancing diaphragm I2. A chamber I4 under diaphragm I2 is provided with a vent connection I8. If the engine is supercharged, this connection should lead to the impact tube 22. Otherwise, the vent connection may *lead to the atmosphere or to any other suitable source of substantially constant pressure. The valve I8 is biased toward closed position by a spring 18 retained between the diaphragm I2 and a retainer 88 having a projection 82 which engages and serves as a follower for a cam 84. The pump inlet pressure acts upwardly on valve I8 and downwardly on the equivalent area of.

diaphragm I2. The valve is therefore balanced against pump inlet pressure. The pump discharge pressure acts downwardly on valve 18 and is opposed by spring I8 and the pressure in chamber 14. The pump discharge pressure moves the valve 18 downwardly, thereby opening it and reducing the pump discharge pressure until that pressure balances the force of spring I8. Hence the cam 84, thru its control of the force of sprin I8, controls the pump discharge pressure.

The cam 84 is driven by a reversible motor 88. Motor 88 is controlled by a pair of relays 88 and 88. Relay 88 includes a winding 82 which controls the movements of a switch arm 84 between a back contact 88 and a front contact 88. Relay 88 includes a winding I88 which controls the movements of a switch arm I82 between a bacl; contact I84 and a front contact I88.

When winding 82 of relay 88 is-energized, switch arm 84 engages contact 88 whereupon an energizing circuit for motor 88 is completed from a supply line L1 through a conductor I88, contact 88, switch arm 84, conductor H8, and motor 88 to supply line L2.

When winding I88 of relay 88 is energized, switch arm I82 engages contact I88, thereby completing and energizing circuit for motor 88 from supply line L1, through a conductor II2, contact I88, switch arm I82, conductor H4; and motor 88 to supply line L2. The two circuits just traced include separate windings of motor 88, which,

when energized, cause operation of the motor 88 in opposite directions.

When both winding 82 of relay 88 and winding I88 of relay 88 are de-energized, both windings of motor 88 are connected in series in a circuit which may be traced from motor 88 through conductor I I8, switch arm 84, contact 88, conductor II8, contact I84, switch arm I82 and conductor II4 back to motor 88. This provides a dynamic braking circuit for the motor, so that the motor quickly comes to a stop whenever both relay windings are de-energized.

The control device 38 includes a chamber II8 separated from chamber 38 by a flexible diaphragm I28. It also includes a chamber I22 separated from chamber 28 by flexible diaphragm I24. Chamber H8 is connected through a conduit I28 to the fuel supply line at the upstream side of the restriction 54. Chamber I22 is connected through a conduit I28 to the fuel supply line at the downstream sideof the restriction 54. The central portions of the diaphragms I28, 38 and I24 are connected by a stem structure I38, so that all the diaphragms move in unison. Inside the chamber II8, the stem structure I38 .carries a movable condenser plate I32. Another movable condenser plate I34 is carried by the stem structure I38 inside the chamber I22.

The condenser plate I32 co-operates with a 4 stationary condenser plate I38, and with it forms a variable condenser generally indicated at I38. The movable condenser plate I34 co-operates with a stationary condenser plate I48, and with it forms a variable condenser generally indicated at I42.

The pressure regulator 58 includes a diaphragm I44 separating a pair of expansible chambers I48 and I48. A valve I58 is carried at the center of diaphragm I44. A spring I52 biases valve I58 toward closed position. The chamber I48 is vented at I54. The vent I54 should lead to the same place as the vent connection 78 on the pump 52. Chamber I48 is connected to conduit 88. The valve I58 is positioned in accordance with the balance between the pressure in chamber I48 and the spring I52. The pressure in chamber I48 is so much lower than the pressure in chamber I48 and the s.rength of spring I52 that it may be neglected. The valve I58 maintains a substantially constant pressure in chamber I88, depending upon the strength of spring I52. In this way, variations in pressure at the discharge nozzle I8 are prevented from affecting the pressure on the downstream side of metering restriction 54, and thereby disturbing the metering characteristics of that restriction.

Figure 2 There is illustrated in Figure 2 a modified form of motor control system which may be used In place of the motor 88 and the relays 88 and 88 of Figure 1. In Figure 2 there is shown a continuously running motor 288 which drives a gear 282. Gear 282 engages a gear 284 and an idler gear 288, through which it drives a gear 288. A

pair of electromagnets2l8 and 2I2 are provided to operate a pair of clutches 2 and 2I8. When electromagnet 2I8 is energized, it operates clutch 2I4 to connect gear 288 with a gear 2I8. When electromagnet 2 I2 is energized, it operates clutch 2I6 to connect gear 288 with a gear 228. The gears 2I8 and 228 both engage a gear 222 on the shaft of cam 84. It may therefore be seen that when electromagnet 2 I8 is energized, the cam 84 is driven in one direction and when electromagnet 2I2 is energized, the cam 84 is driven in the opposite direction. The windings of electromagnets 2I8 and 2E2 may be energized in the same manner as the windings of relays 88 and 88 of Figure 1.

Figure 3 The wiring diagram of Figure 3 shows a bridge circuit 388 having a pair of input terminals 802 and 384 and a pair of output terminals 888 and 388. The input terminals 382 and 388 are connected by conductors 3I8 and 3i 2, respectively, to taps 3I4 and 3I8 on the secondary winding 3 I8 of a power input transformer 328. The trans former 328 has a primary windin 322 connect= ed to the power supply lines L1 and L2. The out put terminals 388 and 388 of the bridge circuit are connected to the terminals of the primary winding 32% of an output transformer 328 by means of conductors 32'l and 328, respectively. Transformer 328 has a secondary winding 328.

A full-wave rectifier circuit is connected between the conductors 3I8 and M2 and a center tap 338 on the transformer winding 3; to provide a unidirectional biasing potential across a resistance 332. One half of the rectifier circuit may be traced-from tap 3I4 through conductor 3I8, a conductor 334, the anode 336 of a double diode indicated generally at 388, cathode 348, a

conductor 342, resistance. 332 and a conductor 344 to tap 336. The other half of the rectifier circuit may be traced from tap 316 through conductor 2, a conductor 346, anode 348, cathode 356, conductor 342, resistance 332 and conductor 344 to tap 336. A filter condenser 352 is provided in parallel with resistance 332 and another filter condenser 354 is connected between one end of resistance 352 and a movable tap 356.

It will be readily understood that the two halves of the rectifier circuit described above rectify opposite half cycles of the applied potential, and a substantially unidirectional potential is thereby secured across resistance 332. By moving the tap 356 along the resistance 332, a varying amount of this unidirectional potential may be secured between the tap 356 and the right-hand terminal of resistance 332.

The secondary winding 328 of transformer 326 and the portion of resistance 332 between the tap 356 and its right-hand terminal are connected in series in a common branch of the input circuits of a pair of gas-filled electrical discharge devices 358 and 366. These devices may be of the well-known Thyratron type. The device 358 includes an anode 362, a pair of control electrodes 364 and 366, and a cathode 368. The device 366 includes an anode 316, a pair of control electrodes 312 and 314, and a cathode 316.

The input circuit of the discharge device 358 may be traced from control electrode 366 through conductors 318 and 386, secondary winding 328. a conductor 382, tap 356 and the right-hand portion of resistance 332, conductors 384 and 386, condenser 388 and resistance 396 to cathode 363. The output circuit of the discharge device 356 may be traced from anode 362 through a conductor 392, the upper half of secondary winding 3i8, tap 336, conductors 344, 384 and 386, condenser 388 and resistance 396 to cathode 368.

The input circuit of discharge device 366 may be traced from control electrode 314 through condoctors 394 and 386, secondary winding 328, conductor 382, tap 356, the right-hand portion of resistance 332, conductors 384 and 396, a condenser 398, and a resistance 466 to cathode 316. The output circuit of the discharge device 366 may be traced from anode 316 through a conductor 462, the lower half of secondary winding 368, conductors 344 and 384, conductor 396, condenser 388, and resistance 466 to cathode 316.

(Zonnected in series across the terminals of condenser 388 are a gas-filled diode 462 and the relay winding 92 of Figure 1. Similarly connectcd in series across the terminals of condenser 396 are a gas-filled diode 464 and the winding 666 of relay 96 of Figure 1. These diodes have a characteristic, well known in the art, that a higher potential is required to initiate a discharge thru them than is required to maintain the discharge after its initiation.

Operation The variable condensers I38 and I42 are connected in adjacent arms of the bridge circuit 366. The variable condenser 48 is connected in a thirdarm, and a manually variable condenser 368 is connected in the fourth arm of the bridge circuit 366. The condenser 369 is adjusted so that when the air and fuel flows balance each other, the bridge circuit is balanced and therefore the electrical potential appearing between its output terminals is zero. There is therefore no potential induced in secondary winding 328.

If it is assumed that there is initially no charge of the condensers 381 and 398, then the only potential impressed on the input circuit of the discharge devices 358 and 366 is the positive biasing potential between the tap 356 in the right end of resistance 332. This renders the discharge devices 358 and 366 conductivx during the respective half cycles during which they may be conductive due to their opposite connection to the transformer winding. As the discharge devices conduct, they build charges on the condensers 388 and 398. If the charge of condenser 388, for example, exceeds a predetermined amount determined by the characteristics of relay winding 92 and the diode 462, then the condenser 388 discharges to diode 462 and winding 92, thereby momentarily energizing winding 92 and operating the relay 88 to energize motor 86 for operation in one direction. Winding 92 is energized for a period long enough to reduce the terminal voltage of condenser 388 below the value required to maintain diode 462 conductive. However, as the charge builds up on condenser 388, it supplies an additional negative potential to the control electrode 366, because the left terminal of condenser 388 is negative, since current flows through the discharge device 358 only in the direction from the anode to the cathode. If the only potentials appearing in the input circuit of the discharge device 358 are the potential across the condenser 388 and the biasing potential of resistance 332, then the potential across condenser 388 will build up either until it discharges through diode 462 or until it becomes sufiiciently great to bias the discharge device 358 to cut-off. The tap 356 of resistance 332 is preferably so adjusted that the potential of condenser 388 completely opposes it and biases the discharge device 358 to cut-off just before the potential of condenser 388 becomes large enough to cause a discharge through diode 462. A similar situation exists with respect to condenser 398 and discharge device 366.

The normal state of affairs when the bridge circuit is balanced is then to have condensers 388 and 396 charged almost but not quite enough to discharge across the diodes 462 and 464, respectively. Under such conditions, if the bridge circuit becomes unbalanced, which may be due to either the air or fuel flow becoming too large with respect to the other flow or to a variation in the density of the air, then an output potential appears between output terminals 366 and 368 of the bridge circuit. This output potential is amplified by transformer 326 and the amplified poteniial appears in secondary winding 328. the bridge circuit is unbalanced in one direction, this potential will have a certain phase, and if the bridge circuit is unbalanced in the opposite direction, this potential will have the opposite phase, in accordance with the well-known characteristics of alternating current bridge circuits. Whichever phase it has, it will be the same as the phase of the power voltage applied between anode and cathode of one or the other of the two discharge devices 358 and 366. If it appears to be out of phase with both of these voltages, then suitable phase shifting or networks may be introduced to correct the situation.

In any event, the potential induced in secondary winding 326 adds a positive potential to the control electrodes 366 and 314 during the half cycle when one or the other of the two di charge devices 358 and 366 may become conductive. Therefore, one of the two discharge devices will conduct, thereby increasing the charge on its associated'con'denser lll or ill, and building up that charge to apoint where the condenser discharges through the diode andthe as sociated relay windings to cause operation or the motor. The relay windings and the motor windings are so connected that the motor is thereby driven in a direction to vary the fuel flow so as to correct the balance between the air and fuel flows and restore the balance of the bridge circuit. i

It may be seen that after one discharge or the condenser ill, the motor cannot receive another energizing impulse until the condenser lll has had time to recharge. Therefore, the' motor is energized in intermittent pulses. The time between these pulses depends upon the electrical characteristics of the condenser 308 and the resistance ill, and the circuit in which they are connected. It should further be noted that ii the bridge circuit remains unbalanced, that is, if the first pulse is not suflicient to correct it, then the unbalance of the bridge circuit increases the conductivity of the affected discharge device, and thereby increases the charging rate of the condenser associated with it. The greater the unbalance of the bridge circuit, the greater the increase in the charging rate of the condensers, and the taster the pulses come one after the other. The circuit may be arranged so that upon extreme unbalance of the bridge, the charging rate is suflicient to maintain a continuous flow thru the diodes and relays, and hence to maintain the motor continuously energized. Therefore, it may be seen that the motor 88 is driven in a direction depending upon the direction of unbalance of the bridge circuit and at an average rate which depends upon the magnitude of unbalance of the bridge circuit. The unbalance of the bridge circuit is in turn an indication of the unbalance between the fuel fiow and air flow in the carburetor.

If one oi the discharge devices 358 or 360 is tripped due to a stray electrical impulse entering the system, then the erroneous tripping oi the discharge device cannot be repeated until a suificient time has passed-tor the charge on the condenser to build up again. This time element also gives the system time to react to thetripping of the relay so as to unbalance the bridge cire cuit slightly and cause a tripping of the opposite relay to restore the balance condition. It may therefore be seen that the control circuit shown is very stable and that it is not subject to severe disturbance by undesired outside influences.

It should also be noted that after an unbalance of the bridge circuit, the motor is slowed down as the bridge circuit approaches its balanced condition, thereby preventing the system from overshooting, which is a common fault of electrical motor control systems.

Movement of the tap 356 along resistance 332 varies the positive biasing potential applied to the control electrodes 366 and 314. This varies he sensitivity of the system in that it determines the minimum unbalance of the bridge circuit which will cause an operation of the motor.

Movement of tap 356 also regulates the sensitivity of the system to stray impulses. The po-, sition of tap 356 determines the potential across the condensers 388 and 398 under normal balanced conditions. It therefore determines the difierence between that normal potential and the potential on those condensers which will trip their associated thyratrons. A stray impulse can only cause operation of the motor it its duration is sufllcient to charge the condensers to the tripping potential. In this way, the stability of the system in the presence 01' stray impulses is greatly increased.

The terms and expressions which I have employed arefor use as terms of description and not of limitation, and I have no intention in the use of such terms and expressions, of excluding any equivalent of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invented claims.

I claim as my invention:

1. Control apparatus including reversible motor means having a pair of windings to be selectively energized in accordance with the direction of departure of a variable condition from a predetermined value, an energizing circuit for each of said windin s including a first gas-filled electric discharge device having a pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being eflective when the potential across it exceeds a value predetermined by the characteristics of 'said device and said winding to discharge thru a positive biasing potenial opposed to said condenser potential, means in said last-named connecting means for introducing therein a signal potential varying in polarity in accordance with the direction of departure of said condition from said value, a source of alternating electrical energy, means connecting the anodes and cathodes of said second discharge devices to said source in phase opposition, and means for varying said positive biasing potential with respect to said predetermined value of condenser potential to control the sensitivity of response of said control apparatus to said signal potential.

2. Control apparatus including reversible motor means having a pair of windings to be selectively energized in accordance with the direction oi departure of a variable condition from a predetermined value, an energizing circuit for each of said windings including a gas-filled electric discharge device having a pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being eilective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge thru said device and said winding, thereby energizing said winding, and means for selectively charging the condensers in said circuits in accordance with the direction of departure of said condition from said value.

3. Control apparatus including reversible motor means having a .pair of windings to be selectively energized in accordance with thedirection and magnitude of departure of a variable condition from a predetermined value, an energizing circuit for each 01' said windings including .a gasillled electric discharge device having a pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being eflective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge thru said device and said winding, thereby energizing said winding, and means for selectively charging the condensers in said circuits in accordance with the direction of departure of said condition from said value, and for varying the rate of charge oi said condensers in accordance with the magnitude of departure or said condition from said value.

4.'Control apparatus including an electrical winding to he intermittently energized in accordance with the magnitude of departure 01' a variable condition from a predetermined value, an energizing circuit for said winding including a gas-filled electric discharge device having a pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being effective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharg thru said device and said winding, thereby energizing said winding, means for charging said condenser, means for varying the rate of charge in accordance with the magnitude of departure of said condition from said value.

5. Control apparatus including reversible nio= tor means having a pair of windings to be selec= tively energized in accordance with the direction or departure of a variable condition from a predetermined value, an energizing circuit for each of said windings including a gas-filled electric discharge device having a pair oi electrodes connected series with said wininng, a condenser connected in parallel with said winding and said electrodes in series, said condenser being effective when the potential across it exceeds a value predetermined by the chaarcteristics of. said device and said winding to discharge thru said device and said winding, thereby energizing said winding, means for charging said condenser including a second gas-filled electric discharge device having an anode, a cathode and acontrol electrode, means connecting one terminal of said condenser to said cathode, means connecting the other terminal of said condenser to said anode, means connecting said other terminal to said control electrode so that the potential across said condenser biases said control electrode negatively with respect to said cathode, means in said last-=, named connecting means for introducing therein a positive biasing potential opposed to said condenser potential and having a value sufficiently smaller than said predetermined value of condenser potential so that said condenser potential biases said discharge device to cut off before said condenser is charged to said predetermined value when said condenser potential and said biasing potential are the only potentials in said last-named connecting means, means in said last-named connecting means for introducing therein a signal potential varying in polarity in accordance with the direction of departure of said condition from said value, and means for varying said positive biasing potential with respect to said predetermined value of condenser potential to control the sensitivity of response of said control apparatus to said signal potential.

Sill

6. A fuel supply system for an internal combustion engine, comprising means for measuring the rate of flow 01' combustion air to said engine, means for measuring the rate 01' now of fuel to said engine, first and second variable condensers, means including both said measuring means for simultaneously and oppositely varying the capacitance of said condensers in accordance with the balance between said air and tuel flows, a third variable condenser, means density of said combustion air for varying said third condenser, a bridge circuit, means con-' necting said first and second condensers in adjacent arms of said bridge circuit, means connecting said third condenser in another arm of said bridge circuit, and means responsive to the unbalance potential of said' bridge circuit for controlling the flow oi i'uel to said engine.

7. A fuel supply system for an internal combustion engine, comprising means for measuring the rate of flow of combustion air to said engine, means for measuring the rate oi. flow of fuel to said engine, first and second variable condensers, means including both said measuring means for simultaneously and oppositely varying the capacitance of said condensers in accordance with the balance between said air and fuel flows, a third variable condenser, means responsive to the density of said combustion air for varying said third condenser, a bridge circuit, rneam con-= necting said first and second condensers in adjacent arms of said bridge circuit, means con necting said third condenser in another arm of said bridge circuit, means for controlling the v of fuel to said engine includinc reversible r means having a pair of windings to ice-selectively energized to cause operation said iuel. flow control means in opposite directions, an ener gizing circuit for each of said windings a first gas-filled electric discharge device a pair of electrodes with said winding, a fixed condenser connected in parallel with said winding said electrodes in series, said fixed condenser being eilective when the potential across it exceeds a value predetermined by the characteristics or" said device and said winding to discharge thru device and said winding, thereby energizing said winding, means for charging said fixed condenser including a second gas-filled electric discharge device having an anode, a cathode and a control electrode, means connecting one terminal of said fixedcon-= denser to said cathode, means connecting the other terminal of said lined condenser to said anode, means connecting said other terminal to said control electrode so that the potential across said fixed condenser biases said control electrode negatively with respect to said cathode, means in said last-named connecting means for introducing therein a positive biasing potential onposed to said fixed condenser potential, and means in said last named connecting means for introducing therein a signal potential varying in polarity and magnitude in accordance with the unbalance potential of said bridge circuit, and means for varying said positive biasing pc== tential with respect to said predetermined value of condenser potential control the sensitivity of response of said fuel now control means said signal potential.

8. carburetor for internal combustion engines comprising an air supply and a Zuel supply, means for measuring the rates oil .flow oi saidair and fuel supplies, means for balancing said measurements against each other, and lectron c responsive to the of said measurements, for controlling the rate" of fuel flow; said control means including reversible motor means having a pair of windings to be selectively energized in acordance with the direction of departure of said measurements from a predetermined balance, an energizing circuit for each of said windings including a gas-filled eletcric discharge device having a pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being eifective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge through said device and said winding, thereby energizing said winding, and means for selectively charging the condensers in said circuits in acordance with the direction of departure of said measurements from said balance.

9. A carburetor for internal combustion engines comprising an air supply and a fuel supply, means for measuring the rates of flow of said air and fuel supplies, means for balancing said measurements against each other, and electronic means, responsive to the balance or unbalance of said measurements, for controlling the rate of fuel flow; said control means including reversible motor means having a pair of windings to be selectively energized in accordance with the direction of departure of said measurements from a predetermined balance, an energizing circuit for each of said windings including a first gasiilled electric discharge device having a, pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said eletcrodes in series, said condenser being eifective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge through said device and said winding, thereby energizing said winding, means for charging said condenser including a second gasfilled electric discharge device having an anode, a cathode and a control electrode, means connecting one terminal of said condenser to said cathode, means connecting the other terminal of said condenser to said anode, means connecting said other terminal to said control electrode so that the potential across said condenser biases said control electrode negatively with respect to said cathode, means in said last-named connecting means for introducing therein a positive biasing potential opposed to said condenser potential, means in said last-named connected means for introducing therein a signal potential varying in polarity in accordance with the direction of departure of said measurements from said balance, a source of alternating electrical energy, means connecting the anodes and cathodes of said second discharge devices to said source in phase opposition, and means for varying said positive biasing potential with respect to said predetermined value of condenser potential to control the sensitivity of response of said control apparatus to said signal potential.

10. A carburetor for internal combusion engines comprising an air supply and a fuel supply, means for measuring the rates of flow of said a7; and fuel supplies, means for balancing said measurements against each other, and electronic means, responsive to the balance or unbalance of said measurements, for controlling the rate of fuel flow; said control means including reversible motor means having a pair of windings to be selectively energized in accordance with the direction and magnitude of departure of said measurements from a predetermined balance, an energizing circuit for each of said windings including a gas-filled electric discharge device having a pair of electrodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being effective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge through said device and said winding, thereby energizing said winding, and means for selectively charging the condensers in said circuits in accordance with the direction of departure of said measurements from said balance, and for varying the rate of charge of said condensers in accordance with the magnitude of departure of said measurements from said balance.

11. A carburetor for internal combustion-engines comprising an air supply and a fuel supply, means for measuring the rates of flow of said air and fuel supplies, means for balancing said measurements against each other, and electronic means, responsive to the balance or unbalance of said'measurements, for controlling the rate of fuel flow; said control means including an electrical winding adapted to be intermittently energized in accordance with the magnitude of departure of said measurements from a predetermined balance, an energizing circuit for said winding including a gas-filled electric discharge device having a pair of electrodes connected in series with said winding, a, condenser connected in parallel with said winding and said electrodes in series, said condenser being effective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge through said device and said winding, thereby energizing said winding, means for chargin said condenser, means for varying the rate of charge in accordance with the magnitude of departure of said measurements from said balance.

12. A carburetor for internal combustion engines comprising an air supply and a fuel supply, means for measuring the rates of flow of said air and fuel supplies, means for balancing said measurements against each other, and electronic means, responsive to the balance or unbalance of said measurements, for controlling the rate of fuel flow; said control means including reversible motor means having a pair of windings to be selectively energized in accordance with the direction of departure of said measurements from a predetermined balance, an energizing circuit for each of said windings includin a first gas-filled electric discharge device having a pair of elec--' trodes connected in series with said winding, a condenser connected in parallel with said winding and said electrodes in series, said condenser being effective when the potential across it exceeds a value predetermined by the characteristics of said device and said winding to discharge through said device and said winding, thereby energizing said winding, means for charging said condenser including a second gas-filled electric discharge device having an anode, a cathode and a control electrode, means connectin one terminal of said condenser to said cathode, means connecting the other terminal of said condenser to said anode, means connecting said other terminal to said control electrode so that the poten tial across said condenser biases said control electrode negatively with respect to said cathode, means in said last-named connecting means for introducing therein a positive biasing potential opposed to said condenser potential and having a value sufficiently smaller than said predetermined value of condenser potential so that said condenser potential biases said discharge device to cut off before said condenser is charged to said predetermined value when said condenser potential and said biasing potential are the only potentials in said last-named connecting means, means in said last-named connecting means for introducing thereina signal potential varying in polarity in accordance with the direction of departure of said measurements from said balance, and means for varying said positive biasing potential with respect to said predetermined value of condenser potential to control the sensitivity 14 of response of said control apparatus to said sig nal potential.

DAVID H. SIEBENTHALER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,911,656 Van Benschoten May 30, 1933 1,960,350 Shackleton et al. May 29, 1934 2,154,375 Chambers Apr. 11, 1939 2,372,766 Colvin et al Apr. 3, 1945 2,395,648 Teichert Feb. 26, 1946 2,482,254 Fairchild Sept. 20, 1949 2,488,221 Moore Nov. 15, 1949 

